Yahoo! PlaceFinder is a REST web service that will turn an address into the latitudinal and longitudinal coordinates in XML, JSON, or serialized PHP objects. It has a few other functions too, like finding the nearest airport, time zone, and even telephone area code. [...] PlaceFinder is a very simple REST service, so cURL is a quick and easy way to access it. There are no authentication tokens to deal with or logon procedures. Just send a GET request, and read the response.

He links you to the service to get an API key and includes a simple class (PlaceFinderAPI) that builds the GET query for you and makes the request via curl. Also included is an example showing how to find a given location (coincidentally, his location choice is the hotel where the php|tek conferences are held).